The present invention relates to the field of corrugated cardboard production; more particularly, the present invention relates to devices for scoring corrugated cardboard.
In the corrugated cardboard industry, grooving or scoring is produced automatically in the longitudinal direction of the machine by means of scoring blades or rings. This scoring, which provides grooves or creases which determine where the cardboard blank is to be folded subsequently, is especially critical and produces uncontrolled gap widths in the finished folded box according to the state of the art today. This is solely the result of unsatisfactory scoring.
Scoring is performed in the longitudinal direction of the corrugated cardboard and thus longitudinally to the corrugations in the cardboard, therefore always encountering different conditions from the peaks to the valleys of the corrugations. Since the cardboard is folded over belts, a phenomenon called fish-tailing occurs when the folding runs slightly towards the rear in the case when the embossing of the corrugations is less than 100%.
The embossing of the corrugations is also influenced by the grade of paper used. Lightweight paper and recycled grades of paper cannot be embossed to the full extent because these types of paper easily develop cracks and thus reduce the loading capacity of the folded boxes.
German Patent 31 38 454 C2 discloses a device and a method for scoring corrugated cardboard for creating folding grooves for folding and maintaining the dimensions of the cardboard for use with corrugated cardboard scoring machines, where the corrugated cardboard or the cardboard which is to be provided with grooves is passed between two rolls and is thereby scored. The distance between the two rolls is adjusted in advance according to the thickness of the cardboard to be scored, so that the correct pressure is applied to the material to be scored.
German Patent 36 17 916 A1 discloses a method and a device for producing corrugated cardboard blanks for folded boxes, where the blank is conveyed through a feed station, stamping station, a cooling station, a punching station and a discharge station in succession with the help of a conveyor device. Such a machine is known as an in-line machine, because several operations are carried out in one machine. The stamping station of this device has a hydraulically or mechanically driven stamping press with a stationary base plate and a vertically movable upper pressure plate for applying bent edges to predetermined positions on the blank sheets under local effective pressure. Both plates have heating plates whose temperature can be adjusted independently of the other. Since the heating plates are mounted on the stamping die, the scoring is always accompanied by heating and thus is a stationary process. The machine must operate intermittently, i.e., the conveyor device must first pass a blank sheet beneath the stamping die, then stop to close the stamping die and remain closed until the heating plates have been adequately heated. Then the stamping force is increased to stamp the scoring lines. Then the stamping die opens and the conveyor device starts up again, conveying the blank sheet thus scored to the cooling station. One disadvantage of this known device and the method that can be carried out with it is that the conveyor device must be repeatedly braked and then must start up again, which necessitates frequent braking and deceleration of substantial weights and causes a high power consumption. This also naturally limits the speed of the process.
Finally, German Patent Application 195 38 512 A1 describes a method and a device for creating scored lines in corrugated cardboard for better folding and to maintain the correct box dimensions for in-line machines. Immediately before scoring or during the scoring itself, the part of the corrugated cardboard being scored is heated with the help of a heatable table.
In the case of all the known methods, the scoring is performed as a rotational process and is usually performed in the longitudinal direction of the corrugations in the cardboard, so the scoring point begins at different points in the corrugations. This causes great problems in the so-called gap tolerance, which is very important in automatic packaging because it determines the accuracy in folding the box.
The object of the present invention is to provide a device with which more accurate scoring of corrugated cardboard can be achieved than in the related art for the subsequent production of folded boxes. A device having the features of the independent patent claims are used to achieve this object. Advantageous embodiments of the present invention are derived from the dependent claims.
Although the corrugated cardboard is conveyed with a rotating ring in the present invention, the actual scoring is created by a varying number of straight lines or sides, the exact number of sides depending on the outside diameter of the ring.